I thought I'd provide a brief update on the campaign, mainly to say thanks for all the help so far and also to beg for continuing -- ideally even denser -- coverage.

For our Chandra ToO observations, we need to catch YZ Cnc somewhere near the peak of a normal outburst. This is obviously quite difficult, given how short they are. I *almost* triggered on the first normal outburst after the last super, but it turned out I was in transit from the UK to the USA at exactly the time I would have had to be doing this. Murphy's Law.

In any case, in order for this trigger to work, super-early notification of the start of an outburst is critical. Only amateur astronomers will be able to provide that for us. We have a special protocol in place with Chandra that will hopefully ensure that our trigger is successful, but it really rests *crucially* on that early notice. So really dense coverage of the rise and early notifications are central to our entire program.

Again, thanks to all who have already contributed, but please keep going -- the campaign is still going, and I will definitely let you know once we have triggered and we are done. In the absence of such a note from me, you can assume that we have not yet been able to find trigger the X-rays early enough, so our attempt to get this will continue until we do.

I am really grateful for all your help -- campaigns like this would be impossible without you!

AAVSO Special Notice #428 reports that the beginning of the Chandra-observable window for YZ Cnc has been delayed for about a week. Please see the notice for campaign-related details and observing instructions.

Just a reminder: starting tomorrow, Chandra triggers on YZ Cnc are potentially feasible again, so if you can maintain or restart dense coverage and let me know asap about rises to outburst, it would be hugely appreciated. Uploading observations to the AAVSO quickly is a big help also, as their LCG tool is very useful for judging trigger criteria.

YZ Cnc currently seems to be displaying some rather interesting and unusual variability behaviour *in quiescence*, with excursions/flares of up to ~0.5 mag. However, it seems to me that a rise to <14 mag is still a sensible criterion for expecting a trigger.

Just an update on the Chandra YZ Cnc situation: I've heard back from head-quarters and apparently -- due to technical constraints -- they couldn't trigger right now. I therefore hope and intend to go for the next outburst, provided we can catch it early enough and CXC can process the trigger fast enough. After Feb 10, the technical constraints will be lifted, so this is likely to work out.

CXC tell me that this was an extremely useful test of the "pre-trigger check" procedure though.

Thanks for your continued help with this tricky campaign and please continue to monitor YZ Cnc closely if you can!

just a reminder that Chandra should now be able to trigger on YZ Cnc
again, so I am planning to trigger on the next outburst that we catch
fast enough and that Chandra headquarters think they can move on fast
enough.

It looks to me like the next rise should not be far off, so if you can
once again get dense monitoring of the system, upload to the AAVSO, and
notify me personally when it looks like we're heading up, I would hugely
appreciate it!

Good luck on this observation! I really hope you guys can get exiting data from Chandra. Nights are cloudy here in Bloomington (very frustrating, after blue skies during the day) but there seems to be plenty of good coverage from around the world.

Also, would BVRI time series be useful? Or would it be better to have denser V-only time series?

thanks so much for the hard work in covering this outburst -- the
ground-based data we are getting from the amateur community look
fantastic. Chandra did trigger near the peak, and those observations are
in the bag. It would be great if the dense monitoring could continue at
least until the decline is completely over and the system is fully back
in quiescence again, just to give us a really clean view of what this
outburst was like.

I'll let you know once I have preliminary results from the Chandra
observation -- as you may recall, the main goal here is to see if we can
detect the soft X-rays that we think should be coming from the boundary
layer between the disk and the white dwarf during an outburst.

A detection would mean that YZ Cnc might be a great target for the
bigger program I am hoping to kickstart, in which we'd cover a full
outburst with everything from radio to X-rays (including UV, soft
X-rays, hard X-rays, ground-based optical and IR, photometry,
spectroscopy, all at high time resolution). A non-detection would mean I
have to find a different target, but would still be scientifically
interesting.

It seems that YZ Cnc is now rising to the next outburst, so the really dense coverage can be dropped. However, it would be nice to keep at least an eye on it with reasonable cadence over this supercycle (i.e. through the next superoutburst).

Thank you all so much for your help -- it's been invaluable! This campaign genuinely wouldn't have worked without you!

just a final update on the YZ Cnc campaign, i.e. the time-critical Chandra observations for which you helped provide the key optical trigger info.

As you may recall, the Chandra observations -- together with the ones on RX And late last year -- were designed to be pathfinders for a much larger program where we would try to get simultaneous, more or less uninterrupted, time-resolved, multi-wavelength coverage of a dwarf nova eruption covering everything from X-rays to radio wavelengths. The purpose of the pathfinder was to check if RX And or YZ Cnc were suitable targets for this -- the point being that we need to be able to detect the very softest X-ray emission with Chandra for any system that would work for the big program.

In this context, the headline news is slightly frustrating: as was the case for RX And, it appears that we did not see significant (very) soft X-ray emission from YZ Cnc. As with RX And, I suspect at the moment that this is simply because interstellar absorption is too strong. The data we obtained is still interesting, of course, and I do intend to publish it and will get back to everybody who contributed at that time.

The bigger picture, of course, is that it's sort of back to the drawing board for me now in terms of finding a suitable target for the big program. On the other hand, the whole point of the pathfinder was to provide this sanity check and avoid us wasting lots of observatory time on unsuitable targets. I expect I'll be hassling you again with pleas for observations once I have figured which object to try next.